SIST EN ISO 7887:2012 PDF

Overview

EN ISO 7887:2011 - Water quality: Examination and determination of colour defines four standardized methods (A–D) for assessing water colour in raw, potable and some industrial waters. The standard covers both simple visual examinations and instrument-based determinations, and preserves compatibility with the traditional hexachloroplatinate colour scale used in water treatment and limnological surveys. Results must include the method used (A, B, C or D).

Key topics and technical requirements

• Four methods (A–D):
  • Method A: Visual examination of apparent colour in a colourless bottle (field or preliminary use). Only apparent colour reported (intensity: nil/pale/light/dark; hue: e.g. yellowish brown).
  • Method B: Determination of true colour using optical instruments (spectrophotometer or filter photometer). Measurements at minimum wavelengths 436 nm, 525 nm and 620 nm (436 nm always used); useful for raw, drinking and low-colour industrial waters.
  • Method C: Instrument determination of true colour referenced to hexachloroplatinate concentration at λ = 410 nm (harmonized with the traditional scale).
  • Method D: Visual comparison with hexachloroplatinate standard solutions (applies to raw and drinking water).
• Sample handling and preparation:
  • Use colourless sampling bottles; maintain glassware clean (e.g., HCl ~2 mol·L⁻¹ or laboratory surfactant), rinse with appropriate water.
  • Samples for Method A: examine soon after collection; storage up to 5 days at 4 °C ± 2 °C in the dark if necessary.
  • For true colour (B, C): filter samples through 0.45 μm membrane to remove suspended matter; prepare optically pure water via 0.2 μm filter and ISO 3696 grade 1 water.
  • Measure pH in parallel (ISO 10523) because colour can be pH-dependent.
  • Optical cell pathlengths may range down to 1 mm for strong colours; if spectral absorption coefficient α